Smoke Diffusion Research Articles

Experimental Study for Smoke Diffusion in a Vertical Cylinder

This experimental study was conducted to investigate the spread of fire smoke through the vertical penetration passage of a skyscraper. Vertical cylinders were used to observe the smoke diffusion phenomenon in the vertical direction, and the conditions of the limited heat source were constructed. Experimental measurements of the vertical diffusion of the plume generated from the pyrolysis source with natural buoyancy was carried out, and the effect of the cylinder wall was observed. The results were compared with the results of the theoretical equations and numerical analysis and analyzed. It was observed that the plume limited by the vertical cylinder tends to diffuse to the periphery while puffing, similar to the open plume at the initial stage generated in the heat source. However, it was observed that the pipe flow developed while moving upward. In addition, as the cross-sectional area decreased owing to the wall surface of the cylinder, and as the calorific value of the heat source increased, the pipe flow developed rapidly. Keywords: Fire Dynamics Simulator, Buoyant Smoke Diffusivity, High-rise Buildings, Vertical cylinder, Confined Environments

A Study on the Delay Effect of Smoke Diffusion by the Installation Intervals and the Blockage Ratio of the Fire Smoke Diffusion Delay Device in a Great Depth Underground Double-Deck Tunnel

A Study on the Delay Effect of Smoke Diffusion by the Installation Intervals and the Blockage Ratio of the Fire Smoke Diffusion Delay Device in a Great Depth Underground Double-Deck Tunnel

Evacuation dynamics with smoking diffusion in three dimension based on an extended Floor-Field model

This paper proposes an extended Floor-Field (FF) model to study the pedestrian evacuation dynamics under the influence of smoke diffusing in three-dimension (3D). In addition to static and dynamic fields, the extended model adopts the smoke and herding fields to reflect pedestrian’s smoke-avoiding behavior and herding behavior. The impact of smoke on pedestrians’ health is also considered. The smoke will reduce the pedestrians’ health point and finally impact their moving ability. Numerical simulations were carried out to study the evacuation dynamics. The influence of the smoke particles producing rate, the initial health point, the critical smoke concentration value, and the herding field on evacuation dynamics were analyzed in detail. Those results could bring some guidance to make the evacuation strategy in the smoke diffusing environment.

Cloud seeding in Necaxa Watershed

Cloud seeding experiments in Necaxa Watershed, in Mexico, were initiated in 1949, and have been carried out long enough to produce statistically significant data. Those meteorological factors which influence the diffusion of Agl smoke in seeding days have been studied. The results were evaluated by a non-parametric statistics technique and it is inferred that a redistribution of the precipitation was probably caused by an overseeding. Statistically it is also inferred that there was a persistence of AgI smoke on days close to those on which cloud seeding operations were conducted.

Prevalence and perception of cigarette smoking among out of school adolescents in Birnin Kebbi, North-western Nigeria.

Introductioncigarette smoking is on the increase among adolescents' especially in developing countries and is a leading cause of premature morbidity and mortality worldwide. Adolescents incorrectly perceive that cigarette smoking is less risky than other behaviors such as alcohol consumption and drug use. This study assessed the prevalence and perception of out of school adolescents on cigarette smoking in Birnin kebbi metropolis of Kebbi state.MethodsThis is a cross-sectional mixed methods study. For quantitative data, respondents were selected using two-staged sampling technique. Semi structured interviewer-administered questionnaire was used. Univariate and bivariate analysis was done as appropriate using Epi-info software. Focus Group Discussion guide was used for qualitative data collection. Narrative synthesis was used for qualitative data analysis.ResultsThe proportion of respondents who had ever smoked cigarettes was 32.2% while 20.8% currently smoke. Most of the respondents (84.1%) perceived that cigarette smoking was harmful and that passive smoking was dangerous to their health (70.8%). Smokers had a significantly lower risk perception about smoking compared to non-smokers (p < 0.005).ConclusionThe prevalence of cigarette smoking among out of school adolescents is high with smokers having lower risk perception compared to non-smokers. There is an urgent need to create awareness about the specific dangers associated with cigarette smoking, the transient nature of its perceived benefits and the fact that the risks associated with smoking are severe.

Numerical Simulation on Smoke Spread and Temperature Distribution in a Corn Starch Explosion

It is discovered from dust explosion accidents in recent years that deep causes of the accidents lies in insufficient cognition of dust explosion danger, and no understanding on danger and information of the dust explosion. In the study, Fire Dynamics Simulator (FDS) evaluation tool is used aiming at Taiwan Formosa Fun Coast explosion accidents. The calculator is used for rebuilding the explosion situation. The factors affecting casualties under explosion are studied. The injured personnel participating in the party are evaluated according to smoke diffusion and temperature distribution for numerical simulation results. Some problems noted in the fire disaster after actual explosion are proposed, rational site analysis is given, thereby reducing dust explosion risk grade.

Influence of Arrangement of Jet Fans on Smoke Exhaust Effect in a Tunnel with Longitudinal Ventilation System

Abstract Based on the multi- scale coupling method which field model and network model are combined, the smoke spread in the underground unidirectional tunnel was studied. We compared with the effect of smoke diffusion during different number of jet fans operated. Results show that when three sets of fans are operated, there is a backlayering of smoke which will influence the simulation of the model, thus we cannot get a steady state of smoke backlayering. When four sets of jet fans are operated, the backlayering of smoke is eliminated, the result of simulation shows more reasonable. However, it is difficult to maintain a steady stratification in the downstream of fire. The results of the study can provide a reference for the design and operation of jet fans in the underground unidirectional tunnels.

A evaluation study of a fire smoke diffusion delay device installed in a great depth underground double deck tunnel

A evaluation study of a fire smoke diffusion delay device installed in a great depth underground double deck tunnel

Extreme weather in 2017: time to take climate change seriously

Extreme weather in 2017: time to take climate change seriously

The Effect of Subway Tunnel Section Shape on the Moving Train Fire Smoke Flow Characteristics

Based on dynamic grid technology, established a full-size model of subway train and the tunnel, the influence of tunnel section shape (circle, rectangle and arch) on fire smoke flow characteristics during the braking and stop process of subway in tunnel after the fire broke out under the bottom of the vehicle while moving is simulated. The computational results show follows: The results show that the shape of the tunnel has a great influence on the flow velocity around the train under the piston wind and smoke characteristics. The range of high temperature smoke in the arch tunnel fire center upstream is smallest at stop instant. The lower bottom space of the rectangular section tunnel is not conducive to the initial high temperature smoke diffusion and even accelerates the combustion of the train. The narrow side waist of the rectangular section tunnel causes the smoke quickly encircling the train body and the piston wind would slow down faster, which will accelerate the smoke deposition, and is not conducive to the smoke flow downstream. The narrow upper space of the arch section tunnel is favorable for the smoke flow downstream, but the smoke flow back early at about 180s. At 360s, the total temperature and concentration of the arch section tunnel is the lowest, and the rectangle is the highest.

A video-based smoke detection using smoke flow pattern and spatial-temporal energy analyses for alarm systems

Detecting smoke during the initial stages is vital for preventing fire events. This study proposes a video-based approach for alarm systems that detects smoke based on temporal features extracted from optical smoke flow pattern analysis and spatial-temporal energy analysis. To do this, it considers various optical characteristics such as the diffusion, color, and semi-transparency of smoke. In the proposed model, smoke-colored pixels are identified via masking in the HSV color space and a temporal frame difference is applied. To extract the temporal feature vectors, we propose a new method that determines the optical flow of smoke by using distinguished texture information by applying a Gabor filter bank with preferred orientations. In addition, when applied to an image that has been temporal-differenced, the energy of the spatial frequencies is fed as another feature into the feature vector. Finally, these features are fed to a support vector machine (SVM) to discriminate our data more thoroughly and provide accurate detection of smoke. Experiments are carried out with benchmark datasets, which show that the proposed approach can work effectively without false alarms.

Negligible Connections? The Role of Familiar Others in the Diffusion of Smoking among Adolescents

How is the delinquent behavior of adolescents influenced by their peers? Previous studies in criminology have primarily focused on the effects of friendship networks on delinquency, but what is less examined is the influence of weaker and often negligible relationships on behavior. In this paper, we explore the effect of familiar others, namely those socio-demographically similar peers who are not connected through friendships, on the behavioral diffusion of smoking among adolescents. Using data from the National Longitudinal Study of Adolescent to Adult Health, we show that, even after controlling for the behavior of friends, the smoking behavior of familiar others has a significant longitudinal effect on adolescents' likelihood of smoking tobacco and marijuana. The results have important implications for expanding our understanding of the social diffusion of adolescent behavior through contextual mechanisms.

Studies on Smoke Temperature Distribution in a Building Corridor Based on Reduced-scale Experiments

A reduced-scale (1:4) building corridor model was prepared to investigate the heat release rate (HRR) and smoke diffusion in a building corridor. Trays with heptane as fuel were used as fire sources. Three different sizes of trays were involved in this study to investigate the different HRRs. The results revealed that fire associated with larger trays exhibited a steeper power-law growth and decay. The temperature distributions in the corridor for the three cases showed similar tendencies. The temperature in the upper part of the corridor was relatively high, which decayed sharply along the corridor. However, the temperature in the lower part of the corridor was approximately the ambient temperature. Numerical simulation was also introduced to obtain more details regarding the temperature. The ceiling temperature was studied by using dimensionless parameters. The correlation between the ceiling temperature and the distance was fitted by using an exponential equation, and significant fitting results were obtained. Moreover, the vertical average temperatures in the corridor were also studied. The result indicated that greater HRRs led to higher vertical average temperatures with steeper growths and decreases.

A Research and Development for the Delay Device Against Fire Smoke Diffusion in Great Depth Underground Double Deck Tunnels

A Research and Development for the Delay Device Against Fire Smoke Diffusion in Great Depth Underground Double Deck Tunnels

Numerical and experimental study on the flow field induced by a train urgently speeding to the rescue station

To simulate the unsteady airflow variations in the main tunnel, transverse alleyways and pilot tunnel of the rescue station as a train with emergency is speeding towards the rescue station, a numerical model using dynamic mesh technique for the train running to the rescue station was carried out. The dynamic variation analysis of velocity field and pressure field in the rescue station reveals some airflow behaviors. Experiments have been conducted in parallel and efforts have been done in order to verify the validity of the simulation by comparing with the experimental data. The results show, when the train runs towards the rescue station, the airflow variations perform complexly. Before the train decelerates, the positive pressure occurs in the whole rescue station, and the highest relative pressure occurs in the main tunnel, so the airflows in transverse alleyways blow from the main tunnel to pilot tunnel with 6.2m/s of the highest average velocity. In the earlier stage of train’s deceleration period, the airflows in transverse alleyways 1–4# reverse their direction and reach −2.5m/s of the highest average velocity. When the train stops in the rescue station, the velocity of airflow in the evacuation platform area blowing from the rear to the front of the train varies between 9m/s and 12m/s, now the pressure difference between the main tunnel and the pilot tunnel is obviously less than that in the period of constant speed, and the airflows in transverse alleyways still blow from the main tunnel with higher pressure to the pilot tunnel with lower pressure, with 3.7m/s of the highest average velocity. As the train stops further, the pressure difference diminishes gradually, so does the airflow velocities in the evacuation platform area and the transverse alleyways, which decreases to 3m/s and 1.9m/s respectively when the train has stopped for 5min. It is suggested that more attention should be paid to the impact which the airflow field variation produced by a train urgently speeding to the rescue station has on the fire smoke diffusion.

대심도 복층터널 화재 시 유입풍속 저감방안 연구

최근 국내 도심지 도로는 빈번한 교통정체가 발생하고 있다. 도심지 교통정체를 해소하기 위한 방안으로 국내에서는 대심도 복층터널에 대한 계획이 이루어지고 있다. 국내에서 계획되는 대심도 복층터널은 소형차 전용으로 계획되며 네트워크형의 구조를 가지고 있어 차량의 출입이 지하공간에서 이루어지고 있다. 이러한 네트워크형 대심도 복층터널은 터널의 단면 및 높이가 일반도로터널 보다 작고 차량의 출입으로 인한 교통풍의 작용으로 화재연기가 터널 승객의 대피보다 빠르게 전파되어 인명피해 발생이 예상된다. 따라서 본 연구에서는 국내 네트워크형 대심도 복층터널에 화재시 화재연기 확산지연을 방지하고자 화재연기 확산지연 장치 작동시 터널 차단면적에 터널 내 작용하는 유입풍의 저감효과를 분석하였으며, 분석결과 터널 차단면적이 50% 이상일 경우 터널 내 작용하는 풍속을 약 21% 저감시키는 효과가 나타났으며, 면적이 50% 이상일 경우 화재 연기의 확산속도를 약 21% 저감시켜 안전한 대피에 도움이 될 것이라 판단된다. Recently, frequent traffic congestion has occurred in domestic urban roads. As a solution for downtown traffic congestion in domestic urban roads, plans for great depth underground double-deck tunnels have been made. Great depth underground double-deck tunnels that have been planned for passenger cars, has the structure of a network type; the entry of vehicles is carried out in the underground space. In these network great depth underground double-deck tunnels, the cross section and the height of the tunnel are smaller than the general road tunnel, and the smoke of a fire will propagate faster than the evacuation of tunnel passengers by the action of the traffic-ventilation and casualties are expected. Therefore, in the present study, an attempt was made to prevent the delay system for fire smoke diffusion at the time of a fire in a domestic network great depth underground double-deck tunnel according to the area of the tunnel block during the operation of the delay system for fire smoke diffusion to analyze the effects of reducing the inflow velocity. When the area of the tunnel block was not less than 50%, the effect of reducing about 21% of the wind speed acting on the tunnel was significant. If the area is more than 50%, the diffusion rate of fire smoke was reduced by approximately 21%, which will be useful for a safe evacuation.

A Novel Indicator of Life-Course Smoking Prevalence in the United States Combining Popularity, Duration, Quantity, and Quality of Smoking.

To develop a smoking indicator that combines the popularity and duration of smoking and the quantity and quality of consumed cigarettes, factors that vary dramatically over time and across generations. We used retrospective reports on smoking behavior and a time series of cigarette tar yields to standardize nationally representative life-course smoking prevalence rates of 11 generations of US men and women, spanning 120 years. For each generation and gender, we related the standardized data with the corresponding rates of smoking-attributable mortality. Our indicator suggests that US cigarette consumption spread, peaked, and contracted faster than commonly perceived; predicts a significantly stronger smoking-mortality correlation than unadjusted smoking prevalence; and reveals the emergence of a delay (by up to 8 years) in premature death from smoking that is consistent with increasing population access to effective treatments. In fact, we show that, among recent cohorts, smoking health-risk exposure is at a historic low and will account for less than 5% of deaths. Relative to unstandardized measures, our novel, standardized indicator of smoking prevalence describes a different history of smoking diffusion in the United States, and more strongly predicts later-life mortality.

A Research for Preventing Smoke Diffusion in Case of Fire in Great Depth Underground Double-Deck Tunnel

A Research for Preventing Smoke Diffusion in Case of Fire in Great Depth Underground Double-Deck Tunnel

林火烟雾图像识别技术研究

森林对于人类的生存和发展有着深远的影响，但森林火灾是森林防护的最大威胁，它不仅可以毁灭森林甚至可以威胁到生命安全，因此如何对森林火灾的发生尽早作出检测和警报，已成为各国研究的重要课题，尤其是森林覆盖率高的国家。本文结合统计理论的思想，提出了基于时间序列分析的森林火灾烟雾图像识别的方法，以时间轴为标尺，对森林火灾产生的烟雾进行记录，作出烟雾扩散曲线，该曲线记录了森林火灾烟雾从无到有再到消失的全过程，将此曲线作为烟雾识别的特征。实验证明，该方法易于掌握，计算工作量小，易于应用推广。 Forest has a profound impact on human survival and development, but the forest fire is the greatest threat to forest protection, which can not only destroy forest, but also threaten life safety. Therefore how to make an early detection and alert when forest fires happen, has become the important topic of various countries’ research, especially the countries with the forest of high cover rate. According to the statistical theory of thought, forest fire smoke image recognition method is proposed based on time series analysis, which with the time axis as the ruler, records the forest fire smoke, and makes smoke diffusion curve. The curve records the whole process of forest fire smoke from beginning to the disappearance, as the smoke recognition feature. Experimental results show that this method is easy to be applied and popularized due to easy grasp and the less work in calculation.

The Numerical Analysis of Flow Field on Warship Deck

This study aims to simulate the exhaust flow field of ship by the method of computational fluid dynamics (CFD) concerning with the interference by exhaust temperature, shape of stack and rolling angles etc.. In this research wind tunnel test for a corvette has been performed to attain associated experimental data, which were used as a reference basis. During simulation process several configurations of stacks have been selected, and combining with various rolling angles, exhaust temperatures and velocities, we have gene- rated numerous cases from which the diffusion paths and temperature distribution of the exhaust flow field can be clearly observed and analyzed. In terms of numerical simulation, the packaged program computational fluid dynamics software has been adopted. The simulation results also possess the same trend as the experimental data, which have initially confirmed the methods developed here can be used for the arrangement of stack and superstructure at the stage of initial and conceptual design of ships. Keywords—computational fluid dynamics, diffusion distribution, wind tunnel test, smoke diffusion, atmospheric pressure. I. Int ro d uct io n